Ice control is a significant and practical concern for many industries. For example, icing on aircraft contributed about 12% of the total accidents that occurred between 1990 and 2000, according to the AOPA Air Safety Foundation accident database.
Icing is most likely to occur when the outside temperature is between 0° C. to −20° C. Icing can cause the formation of ice on airfoils and other surfaces of the aircraft structure, including wings, stabilizers, rudder, ailerons, engine inlets, propellers, rotors, fuselage and the like. Ice on the aircraft surface can distort the flow of air over the wing, rapidly reducing the wing's lift and significantly increasing drag. Wind tunnel and flight tests have shown that frost, snow, and ice accumulations (on the leading edge or upper surface of the wing) no thicker or rougher than a piece of coarse sandpaper can reduce lift by 30 percent and increase drag up to 40 percent. Larger accretions can reduce lift even more and can increase drag by 80 percent or more.
Spraying aircraft on the ground with glycol-based fluids is expensive and detrimental to environment. For example, cleaning a Cessna 172 of ice or light snow might require 10-15 gallons of fluid for a total cost of up to $160; removing light frost on a clear day from a medium-sized business jet might cost $300, and removing freezing rain on a heavy wet snow from the same mid-sized jet may cost close to $10,000.
Chemicals such as derivatives of glycol ethers have also been used to de-ice aircrafts, as they effectively lower the freezing point. Recently, however, Canada has banned 2-methoxyethanol as a de-icing chemical because of environmental concerns.
Anti-icing and de-icing are the two basic approaches to prevent icing for aircraft. Anti-Icing is turned on before the flight enters icing conditions, while deicing is used after ice has built up. There are several types of de-ice and/or anti-ice systems for modern aircraft that are generally categorized as mechanical, chemical and thermal. Specific examples include pneumatic boots, multiple juxtaposed electro-expulsive elements, de-icing fluids, diverted bleed air or hot air from turbine stages, and electrically conducting resistance heating elements. Energy consumption for this equipment is large. For example, the wattage required for an anti-ice system in a typical high-performance single engine or light twin aircraft, using the resistance heaters, is approximately 21,000 watts.
Polyurethane coating is currently applied onto all aircraft exterior surfaces due to the high performance such as durability, weather resistance, chemical resistance, low temperature resistance, corrosion resistance and fluid resistance. However, the polyurethane chemical structure has high surface energy and strong adhesion to the ice due to the hydrogen bonding.
It would be desirable to provide a method of mitigating ice build-up on a substrate using a coating that can significantly reduce the ice adhesion and meet the aircraft coatings material specification requirement.